The monitoring of performance for various types of equipment, such as used in process industries or in building HVAC systems, is frequently limited. The limitations are due to many of the assets not being sufficiently instrumented by sensors for obtaining measurements, such as temperatures, pressures, flow rates, and other important performance impacting parameters. As a consequence, standard monitoring approaches that are based on first principles (e.g. an understanding of physics, mechanics and chemistry for the given equipment and/or process) cannot generally be efficiently applied because such approaches typically require a large number of sensors and intensive knowledge of the modeled system.
Typically, an important monitor function requirement involves determining whether the value of given equipment performance measure represents normal or abnormal behavior. Some equipment vendors provide rating limits for expected performance (referred to generally as reference behavior), but this is not always that case. As a result, there is a need for a new performance measure reference so that equipment performance at any given time may be judged to determine if it is normal or abnormal, such as for use in determining when to perform equipment maintenance on the equipment.